public class BinarySearchTree {
    static class TreeNode {
        public int val;
        public TreeNode left;
        public TreeNode right;

        public TreeNode(int val) {
            this.val = val;
        }
    }
    public TreeNode root = null;
    public boolean search(int val) {
        TreeNode cur = root;
        while(cur != null) {
            if(cur.val < val) {
                cur = cur.right;
            } else if(cur.val > val) {
                cur = cur.left;
            }else {
                return true;
            }
        }
        return false;
    }
    public boolean insert(int val) {
        TreeNode node = new TreeNode(val);
        if(root == null) {
            root = node;
            return true;
        }
        TreeNode cur = root;
        TreeNode parent = null;
        while(cur != null) {
            if(cur.val < val) {
                parent = cur;
                cur = cur.right;
            } else if(cur.val > val) {
                parent = cur;
                cur = cur.left;
            }else {
                return false;
            }
        }

        if(parent.val < val) {
            parent.right = node;
        }else {
            parent.left = node;
        }
        return true;
    }
    public void remove(int val) {
        TreeNode cur = root;
        TreeNode parent = null;
        while(cur != null) {
            if(cur.val < val) {
                parent = cur;
                cur = cur.right;
            }else if(cur.val > val) {
                parent = cur;
                cur = cur.left;
            }else {
                removeNode(parent,cur);
            }
        }
    }
    private void removeNode(TreeNode parent,TreeNode cur) {
        if(cur.left == null) {
            if(cur == root) {
                root = cur.right;
            } else if (cur == parent.left) {
                parent.left = cur.right;
            }else {
                parent.right = cur.right;
            }

        }else if(cur.right == null) {
            if(cur == root) {
                root = cur.left;
            } else if (cur == parent.left) {
                parent.left = cur.left;
            }else {
                parent.right = cur.left;
            }
        }else {
            TreeNode targetParent = cur;
            TreeNode target = cur.right;
            while (cur.left != null) {
                targetParent = target;
                target = target.left;
            }
            cur.val = target.val;
            if (targetParent.left == target) {
                targetParent.left = target.right;
            }else {
                targetParent.right = target.right;
            }
        }
    }
}
